It is now common practice, and it has been for many years, to build commercial buildings of reinforced concrete. Even when buildings are made from structural steel, it is common for the floors between stories to be formed of cast concrete or other fire resistant materials. Even if floors and separating walls are made from materials other than concrete, fire stopping is required by model building codes to prevent a fire from passing through the floor or walls, in order to prevent the spread of fire and to prevent destructive heat and toxic combustion products from spreading dangerously throughout a building.
On the other hand, it is necessary for there to be through-openings in such floors and walls so that electrical wiring and pipes of various types can pass through such floors and walls. The provision of such openings for pipings of various types to pass through walls and floors of course creates problems insofar as the building codes are concerned, because these openings can permit passage therethrough of fire and/or smoke upon destruction of the piping which normally passes through these openings. Therefore, modern building codes require that when a fire or smoke rated floor is penetrated, it must be restored to its original integrity. Penetration can occur when the type of penetrating material, which may be metal, plastic, insulated or glass pipe, insulated cable, etc. is destroyed by a fire.
Model building codes, including the Standard Building Code, emphasize "approved methods" for fire stopping in such situations, such "approved methods" having been tested using nationally recognized standards at a recognized independent third party testing laboratory, such as Underwriters Laboratories, Factory Mutual, etc. As a result, certain manufacturers (such as the 3M Company and Metaline Company) have developed certain intumescent compositions which may be in the form of wrapping tape or which may be dispensed from a tube (such as caulking material is dispensed) for injection into and around openings passing through fire rated walls and floors and outside the pipes which also pass through such openings. Among prior patents which disclose such intumescent compositions are Dietlein et al U.S. Pat. Nos. 4,686,244 and 4,719,251; von Bonin et al U.S. Pat. No. 4,694,030; Merrill U.S. Pat. No. 3,868,346 and Pratt et al U.S. Pat. No. 4,052,526.
The theory is that under severe fire exposure which results in destruction of the piping material and consequent spread of smoke, heat and/or fire through the entire opening, the intumescent material will expand and completely fill the void and thereby restore the integrity of the floor or wall, thereby at least inhibiting the spread of fire and smoke.
In practice, however, it is difficult and time consuming to apply such intumescent material from a caulking gun; and, moreover, because the application is done manually it varies from location to location and even more so among different applicating personnel, so that in many cases the application is not adequate. Another problem in this prior art is the leakage of expanding intumescent material upon being subjected to fire or the heat generated by the fire; even where metallic collars are manually wrapped about the joint to contain the intumescent material, these collars cannot be applied sufficiently tightly to prevent leakage of the expanding intumescent material from the joint. As a result, insufficient expanded intumescent material may remain in the opening to adequately perform its intended function of restoring the integrity of the floor or wall.
Various attempts have been made to solve these problem including those set forth in the various patents to Harbeke U.S. Pat. No. 4,642,956; 4,848,043; 4,850,385; 4,882,886; 4,888,925; 4,916,800 and 4,918,761. However, these attempts have not proven commercially successful to date. Instead, the art continues to use the relatively primitive approach outlined above, although some cast-in-place fire stop couplings are available in the marketplace.